Numerous processes have been proposed for the removal of components from gas streams including liquifaction, adsorption, absorption, momentum separation, and the like. One common procedure is through contact with a liquid sorbent in which the component to be separated is preferentially sorbed. The sorption may be physical sorption in which the component is soluble in the liquid sorbent or chemisorption in which a chemical reaction occurs with the sorbent. For instance, the sorption of sulfur dioxide in water is defined herein as being a physical sorption and the sorption of sulfur dioxide by calcium hydroxide to form calcium sulphite is defined herein as being a chemisorption. The chemisorption may be essentially irreversible, e.g., the reaction of calcium hydroxide with sulfur dioxide to produce calcium sulphite is essentially irreversible, or reversible, e.g., hydrogen sulfide sorption by alkanolamine. The gas liquid contact mechanisms that have been proposed include tray columns, packed columns, spray columns, etc.
Sorption processes have been proposed to remove widely varying components from widely varying gas streams. For instance, the removal of carbon dioxide and/or hydrogen sulfide and/or sulfur dioxide from natural gas, air, flue gas, petrochemical streams, etc. Sorption processes can recover volatilized catalysts from process streams. In many of these sorption processes, commercial viability depends, in part, upon the efficiency and capacity of the liquid sorbent, the ability of the liquid sorbent to be regenerated and the energy consumption of the sorption process. For example, a sorption process should not result in undue pressure drop to the gases being treated, especially with large volume gases such as flue gases, nor should unduly large amounts of energy be consumed in regenerating the liquid sorbent.
One type of apparatus which does not result in undue pressure drop is known as the "Waterloo" scrubber and is described by Spink in "Handling Mists and Dusts", Chemtech. June, 1988, pages 364 to 368. U.S. Pat. No. 4,067,703 discloses a Waterloo scrubber for the removal of particulates. According to the article, U.S. patent application Ser. No. 20963, has been filed on the use of the Waterloo scrubber as a chemical reactor. The Waterloo scrubber comprises a duct in which the gas to be scrubbed flows and atomizing nozzles spray liquid into the passing gas stream. The gas then passes into a turbulent mixing zone (i.e., a slow moving centrifugal fan) which serves to agglomerate the liquid to provide larger droplets that can be readily separated from the system. An entrainment separation zone can follow the turbulent mixing zone for further recovery of liquid. Since much of the liquid can be removed in the turbulent mixing zone, the pressure drop caused by the entrainment separation zone is much less than if the entrainment separation zone was required to remove substantially all of the liquid.
In his article, Spink states that:
"The Waterloo SO.sub.2 scrubber can remove more SO.sub.2 at a much lower L/G [Liquid-to-Gas] ratio than other scrubbers while employing the same scrubbing media." (Page 366)
He reports the use of ammonia, MgO-containing lime, sodium sulfite solution and iron oxide slurry as various reagents for sulfur dioxide removal.
Sorption processes are souqht which effectively use the capabilities of liquid sorbents while still obtaining the benefits of low pressure drop scrubbers such as spray towers and Waterloo scrubbers.